fix(sk_synthesis): Remove cz & ccz from synth gates

We used to apply the SK synthesis algorithm to the CZ & CCZ gates.
This behaviour was inappropriate as these gates are discrete gates,
and should not be approximated like a continuous one (e.g.: rZ(theta)).

The CZ & CCZ should rather be replaced by CX & CCX respectively in the
"Basis Translation" step of transpilation instead.

This commit does this by removing CZ & CCZ from the list of gates to
synthesize, so they will be ignored by the SK synthesis step.

qiskit_alice_bob_provider/plugins/sk_synthesis.py

@@ -76,6 +76,8 @@ def pass_manager(
                 'measure',
                 'measure_x',
                 'delay',
+                'cz',
+                'ccz',
             }:
                 continue
             if instr.num_qubits == 1:
@@ -95,7 +97,7 @@ def pass_manager(
         # List gates to synthesize (all gates except basis gates)
         synth_gates: Set[str] = set()
         for name, instr in get_standard_gate_name_mapping().items():
-            if name in {'measure', 'measure_x', 'reset', 'delay'}:
+            if name in {'measure', 'measure_x', 'reset', 'delay', 'cz', 'ccz'}:
                 continue
             synth_gates.add(name)
         synth_gates -= set(discrete_basis_gates)